This invention relates to processes for forming panels, boards, or other like products having directional strength properties and more particularly to that portion of the process of forming a mat of oriented small pieces of lignocellulosic material prior to pressing the mat to form a reconstituted product.
It has been known for some time that advantageous directional properties may be obtained by directionally orienting the elongated small pieces of the lignocellulosic material in a desired direction as opposed to randomly orienting the pieces. A considerable amount of research has been conducted to develop commercially attractive techniques for directionally orienting the elongated small pieces during the formation of the mat. Most of the research has been directed along two avenues -- (1) mechanical orientation, and (2) electrical orientation.
At the present time reconstituted wood panels are being formed for the commercial market utilizing mechanical orientation of the elongated small pieces.
Our initial research indicated to us that it was feasible to electrostatically orient small elongated lignocellulosic pieces in a strong electric field on a batch basis. A product of commercial quality could be formed utilizing the batch system which is described in our U.S. Pat. No. 3,843,756 granted to Talbott et al on Oct. 22, 1974. FIG. 5 of that patent shows a technique for forming an oriented mat on a continuous basis. Although during our experimentation we found that electrical orientation could be obtained on a continuous basis we were unable to obtain a commercially acceptable product. We found that the orientation results were somewhat erratic and that our good results which we had obtained utilizing the batch system could not be obtained when we went to a continuous system.
We were mystified as to why good results could be obtained in a batch system but that disappointing results were obtained in a continuous system. We initially experimented with the placement of a set of secondary electrode plates into the vacuum box below the moving mat in an attempt to obtain better orientation. However, even the addition of the secondary electrodes below the mat did not bring the continuous process up to our expectations.
Thus one of the principal objects of this invention is to provide a solution to the problem and provide a commercially attractive process for forming an oriented continuous mat of lignocellulosic material utilizing an electric field.
An additional object of this invention is to provide a process for forming a continuous mat of small pieces of lignocellulosic material having uniform orientation in the length direction of the mat.
A further object of this invention is to provide a process for forming a continuous mat of oriented small pieces of lignocellulosic material that is economical and reliable.
These and other objects and advantages of this invention will be apparent upon reading the following description of preferred and alternate embodiments of this invention.